In the related art, there is known a traction control technology that adjusts engine output, motor output, or the like at the time of slip of drive wheels of a vehicle so as to inhibit the extent of slip of the drive wheels to predetermined value or less. One of such a traction control technology known is a technology that corrects slip by controlling output torque of an electric vehicle driving motor when slip of the drive wheels is detected (for example, PTL 1).
The traction control technology of the related art inhibits previously occurring slip by adjusting output or a driving motor or the like when slip of the drive wheels is detected. Thus, initial slip at the start of the vehicle cannot be prevented. Particularly, initial slip increases when a magnetic pickup type-wheel speed sensor is employed because a low speed of the vehicle cannot be detected. For example, when the vehicle starts on a snowy uphill road, the vehicle may not start once the drive wheels slip because compacted snow decreases a road surface coefficient of friction μ.
In order to prevent initial slip at the start of the vehicle, there is suggested a device that computes the road surface coefficient of friction μ from forward and backward and leftward and rightward acceleration to compute a drive torque restriction value for the start of the vehicle on the basis of the estimated road surface coefficient of friction. μ and that inhibits a rise in the output of the driving motor when drive torque is greater than or equal to the drive torque restriction value (for example, PTL 2).